The primary objectives of this work are to examine current knowledge in the field of carcinogenesis and related fields and to identify criteria for the evaluation of carcinogenic effects of chemical and physical agents and for the prevention of cancer hazards in the human population. Laboratory methods and biological models for the detection of carcinogenic activity of chemicals are examined and evaluated, with particular emphasis on in vitro models for carcinogenesis studies and animal models of carcinogenesis. Criteria for the evaluation of carcinogen risk from environmental and occupational human exposures are developed. BIBLIOGRAPHIC REFERENCES: Saffiotti, U.: Experimental approaches to the identification of environmental carcinogens. In Epstein, S. S. (Ed.): Environmental Determinants of Human Cancer. Springfield, Illinois, Charles C. Thomas Publishers, 1977, In press. Saffiotti, U. and Page, N. P.: Releasing carcinogenesis test results: Timing and extent of reporting. J. Med. Pediatr. Oncol., 1977, In press.